Crack Initiation Criteria and Fracture Simulation for Precracked Sandstones

Table 3

Numerical results of stress near the crack tip.

Condition	Crack thickness d (mm)	Crack angle β (°)	Maximum circumferential stress at crack tip (MPa)	Direction of the maximum circumferential stress (°)	Maximum radial shear stress at crack tip (MPa)	Direction of the maximum radial shear stress (°)
1	0.5	15	10.258	13	8.206	0
2		30	13.057	47	10.435	0
3		45	14.984	63	11.981	0
4		60	12.731	65	10.193	0
5		75	11.726	73	9.437	0
6	2.0	15	13.127	34	8.533	−10
7		30	15.424	45	14.677	2
8		45	12.387	81	17.749	7
9		60	7.742	101	17.066	12
10		75	1.548	125	14.678	41

The tip radius of curvature is 0.25 mm for conditions 1–5 and 1.0 mm for conditions 6–10.